Stencil sheet and process for forming the same



Patented- NoV. 21, 1933 s'rENcii. SHEET AND PROCESS FOR FORMING THE SAME Louis Fuller, New York, N. Y.

No Drawing. Application March 19, 1932 a I Serial No. 600,049

. 19 Claims. (01-. ll-38.6)

7 My invention relates to permeable sheets so prepared as to be impervious to ink until pressure has been applied by means of raised characters such as the type of a writing machine, or by means of a stylus, such part of the sheet thereby becoming pervious and so altered that ink will pass. v

My invention may be used in place of and is an improvement over those stencil papers such as wax and others which are easily ruptured in the typing process and which must be carefully handled to avoid injury to the coating. It is also an improvement over that class of stencil-sheets requiring the application of moisture previous to typing, in that while possessing to a marked degree the durability and toughness of such stencil sheets, and while capable of the same excellent and large number of reproductions, it does not require any moistening, this being a distinct advantage.

In general my new stencil sheet is distinguished over all other dry stencil sheets of which I.have ever heard, by the fact that it may be bent, twisted and crushed repeatedly without impairment of its typing qualities and possesses great chemical and mechanical stability. Suitably packed in cartons it will remain usable for long periods of time. In the typing process it also possesses the added improvement over other dry stencil sheets in that it does not clog the type of the writing machine with extractive matter from the substance of the coating.

The object of my invention therefore is the production of an improved stencil sheet which shall be tough and durable, which may be typed in a writing machine without moistening, will afford 'a large number of reproductions and will not deteriorate from long usage. A further object is that the stencil sheet shall be completely proof 40 against ink, this latter quality not being possessed by some of the stencil sheets that have been sold in the market. Unlike other stencil sheets except those requiring moistening prior to typing, my stencil sheet is proof against all neutral solvents or solvents of ink, and in cases where they are kept for reprinting, may be cleansed from ink by means of benzine or oil or a similar substance, without any deterioration of the stencil sheet.

I accomplish this object by making use of the great stability and other desirable properties of certain acid anhydrides when combined homogenously'in a film or coating with other stable substances such as hardened proteins or other colloids, and substances suchas glycerin or its equivalents, a concrete example of said formula being given in thefollowing description. When these substances are brought into solution by means of suitable solvents and applied to a sheet of open, fibrous material such as Japanese Yoshino paper, on evaporation of the solvents a tough and impervious sheet results, which is capable of being typed in the ordinary manner. The acid anhydrides as made by my process and referred to, I have discovered are particularly adapted for use in stencil sheet coatings for the reason thatthey are very stable and easily assimilated by the other ingredients of the film, the whole forming a tolerant mixture which deposits a homogeneous film of great flexibility and toughness,

The most useful of these acid anhydrides'l have found, are those for the manufacture of which I have devised a special process, involving the use of a catalyst and relatively low temperatures, the final product being easy ofipuriflcation. Anhydrides of the formula (R) 20 are obtained, the molecule of the acid or the acid containing substance being doubled if necessary. Acetic anhydride is used in molecular proportions, with an excess sufficient to remove the hydroxyl from the acid, and to react on the C3H5 radical in cases where glycerides are used. The material I prefer to employ is either stearic acid or a compound the principal constituent of which is stearic acid, such as commercial, hydrogenated fatty oil. Such compound is a fatty oil containing more or less unsaturated fatty acids and which upon being hydrogenated or having hydrogen added to the acid radicaL'the fatty acids become saturated and thereby converted into stearic acid.

In operating the process of forming my new stencil sheet therefore I first proceed to manufacture an acid anhydride by reacting on 280 parts of stearic acid and 3 parts of concentrated 95 sulphuric acid, and 90 parts of acetic anhydride, parts being by weight. The stearic acid is introduced warm, into a closed, acid proof container, and while in agitation the mixture of sulphuric acid and acetic anhydride is run in, heating 100 and agitation being continued for about one hour. The reaction takes place practically at atmospheric pressure and the temperature of the mix is maintained at from 120 to 140 degrees F.

.Double relief valves for the purpose of preventing material increase of pressure and formation of a partial vacuum are desirable for the container.

: At the end of one hour a cold, saturated solution of brine is introduced, preferably heated to wateris preferable to allow the mixture to stand about twelve hours as a more complete separation will be obtained.

After complete washing the warm, 'finished stearic anhydride is then drawn 01f, filtered and thus being freed from slight amounts of adhering salt by being allowed to stand in a warm condition, is ready for use. The reaction product may also be freed from acids by other means such as neutralization of th sulphuric acid and distillation and recovery oi. the acetic acid formed, but the means of washing with brine I have found to be preferable.

I then prepare a mixture as follows, parts being by weight. Water 20 parts, denatured alcohol parts, glacial acetic acid 10 parts, glycerine 40 parts, No. lground gelatin 10 parts. This mixture is allowed to stand for about one hour to allow the gelatin to swell or may be agitated by suitable means to save time. The mixture is then warmed to about 100 degrees F. with agitation until the gelatin is dissolved. The solution is then filtered, a suitable coloring matter being added if desired. There is then added to the above solution 40 parts of the anhydride of stearic acid warm, and dissolved inabout 20 parts of benzine and 4 to 5 parts 9f formaldehyde, this latter substance serving to harden the gelatin somewhat. The whole is then well agitated and again warmed if necessary to bring it about 4 90 degrees F.

In the next step of my process the above solution is entered into a suitable pan or tray equipped with a scraping rod or straight-edge, the solution being maintained at around 80 to degreesl The sheets of Yoshino paper are then drawn over the surface of the solution, the surplus being removed by the scraper, and suspended to dry. Om evaporation of the solvents the film sets to a homogeneous compound and in two or three hours the stencil sheets are ready for use.

Sheets are typed in the well-understood manner, being superimposed on heavy paper, a carfier sheet, and are then used in duplicating machines operated by inking pads or rollers for the purpose of making impressions.

The proportions of materials stated in the above solutions may be varied within reasonable limits for the adjustment of the character of the coating, it being understood that the proportion of gelatin, glycerin and acid anhydride are fixed substances that remain in the film to compose the coating of the stencil sheet. Less glycerin and anhydride for example will make a harder film and more a softer'fllm. So that I do not bind myself to these stated proportions of solvents or other substances, it being understood that my process broadly considered, consists of these substances ortheir equivalents .for the purpose of a coating of predetermined character, solvents enough being used to give the necessary fluidity and limpidity to the solution. Part. of the glacial acetic acid and also some.of the alcohol may be replaced by water if desired. These matters will be readily understood by compounders or those skilled in the art.

In place of formaldehyde other hardening agents may be used such as various salts of bath temperature and agitation is continued for the purpose of washing the anhydride free of wise, glycerin and acid anhydride, individually exercise an alternative or tempering effect on each other. The interaction of them produces the completed film possessingthe necessary quality to be permeable in the typing operation.

In the manufacture of the acid anhydride other substances than hydrogenated fatty oil may be used, such as other glycerides or the acids themselves such as stearic, palmitic, oleic or mixtures of these, in each case the necessary molecular quantity of acetic anhydride plus the excess to react on the radical C3H5 if any, being used.

These matters will be readily understood by those skilled in the art.

In the process above stated I may use an acid anhydride made by a different process such as heating in an autoclave for example, my invention of the stencil sheet contemplating such acid anhydride as a necessary ingredient without regard to the process of manufacture.

By omitting the glycerin in the formula above,

I may produce a stencil sheet of hardened protein and acid anhydride alone, more friable, but useful for special typing purposes, without detracting from the substantial part of my invention.

In the process for the manufacture of the acid anhydride above described, I may use other catalysts than sulphuric acid, such as an acid, metallic salt, an oxide, or a catalyst similar to Twitchells reagent. In fact I may use any suitable catalyst having the power to open the molecule of the acid reacted upon and maintain the reaction. The glycerides referred to above means the ordinary fats and oils, containing fatty acids such as those stated, which may also be fatty oils which have had hydrogen added to the molecule, thus becoming more or less saturated compounds such as stearin. The acids mentioned such as stearic, palmitic and oleic are higher fatty acids and my invention comprehends these or their equivalents.

It will be understood thatthe invention of the stencil sheet is not limited to the details as above described but that it comprehends broadly a stencil sheet adapted to be converted into a stencil by pressure, as by impact of type or a stylus thereon, it being essentially a fibrous base provided with a coating which includes suitable anhydrides of the fats and fatty oils or their equivalents, this being so modified as to make it substantially stable for the purpose designed and responsive to pressure for the production of stencil openings of character suitable for the passage of ink.

The invention of the process described herein is not limited to the precise details set forth but comprehends broadly the preparation of the acid anhydride described and compounding it with the remaining ingredients and impregnating open, fibrous material with the completed solution and drying, by suitable, equivalent means.

What I claim is:

1. A stencil blank convertible into a stencil by impact of type and the like thereon, comprising open, fibrous material impregnated with protein and a higher fatty acid anhydride.

2. A stencil blank convertible into a stencil by impact of type and the like thereon, comprising open, fibrous material impregnated with protein, a higher fatty acid anhydride and glycerin.

3. A stencil blank convertible into a stencil by impact of type and the like thereon, comprising open, fibrous material impregnated with protein and stearic anhydride.

4. A stencil blank convertible into a stencil by impact of type and the like thereon, comprising open, fibrous material impregnated with protein, stearic anhydride and glycerin.

5. A stencil blank convertible into a stencil by impact of type and the like thereon, comprising open, fibrous material impregnated with gelatin and a higher fatty acid anhydride.

6. A stencil blank convertible into a stencil by impact of type and .the like thereon, comprising open, fibrous material impregnated with gelatin 9. higher fatty acid anhydride and glycerin.

7. A stencil blank convertible into a stencil by impact of type and the like thereon, comprising open, fibrous material impregnated with gelatin and stearic anhydride.

8. A stencil blank convertible into a stencil by impact of type and the like thereon, comprising open, fibrous material impregnated with gelatin, stearic anhydride and glycerin.

impact of type and the like thereon, comprising open, fibrous material impregnated with hardened protein and a higher fatty acid anhydride.

10. A stencil blank convertible into a stencil by impact of type and the like thereon, comprising open, fibrous material impregnated with hardened protein and stearic anhydride.

11. A stencil blank convertible into a stencil by impact of type and the like thereon, comprising open, fibrous material impregnated with hardened protein, a higher fatty acid anhydride and glycerin.

12. A stencil blank convertible into a stencil by impact of type and the like thereon, comprising open, fibrous material impregnated with hardened protein, stearic anhydride and glycerin.

13. The process of forming a stencil sheet, consisting of heating and agitating a higher fatty acid or a hi her fatty acid containing sub- 9. A stencil blank convertible into a stencil bystance with a dehydrating agent and a catalyst until dehydration of the acid occurs, removing the acids from the resulting acid anhydride, adding thereto protein dissolved in glycerin and suitable solvents and a hardening agent, impregnating an open, fibrous material with the said solution and drying.

14. The process of forming a stencil sheet, consisting of heating and agitating stearic acid with acetic anhydride and concentrated sulphuric acid, as a catalyst until dehydration of the stearic acid occurs, removing the acids from the resulting acid anhydrida'adding thereto a solution of gelatin in suitable solvents and a hardening agent, impregnating an open, fibrous material 7 with the solution and drying.

15. The process of forming a stencil sheet consisting of heating and agitating stearic acid with acetic anhydride and a catalyst such as concentrated sulphuric acid until dehydration of the stearic acid occurs, washing the resulting stearic acid anhydride with brine, adding benzine and a solution of gelatin and glycerin and a hardening agent, impregnating an open, fibrous material with the compound and drying.

16. The process of forming a stencil sheet involving the production and purification of a higher fatty acid anhydride, dissolving in benzine, adding to a solution containing protein and glycerin, impregnating a sheet of open, fibrous material with the solution and drying the sheet.

17. The process of forming a stencil sheet in- 1 volving the production of a higher fatty acid anhydride, washing the same with brine, dissolving in benzine, adding gelatin, suitable solvents and a hardening agent, impregnating an open, fibrous material with the solution and drying.

18. The process of forming a stencil sheet involving the production of a higher fatty acid 115 anhydride, dissolving the acid anhydride in a solution containing gelatin, glycerin, suitable solvents and a hardening agent, and impregnating an open, fibrous material with the solution and drying.

19. The process of forming a stencil sheet involving the production of a higher fatty acid anhydride and dissolving the same in a solution containing protein and glycerin and suitable solvents, coating the solution on fibrous material 125 and drying.

' LOUIS E. FUILER. 

